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From: Peng Zhang <zhangpeng362@huawei.com>
To: <hch@lst.de>, <m.szyprowski@samsung.com>, <robin.murphy@arm.com>,
	<petr.tesarik1@huawei-partners.com>, <iommu@lists.linux.dev>,
	<linux-kernel@vger.kernel.org>
CC: <wangkefeng.wang@huawei.com>, <sunnanyong@huawei.com>,
	<zhangpeng362@huawei.com>
Subject: [PATCH] swiotlb: check alloc_size before the allocation of a new memory pool
Date: Mon, 8 Jan 2024 22:00:05 +0800
Message-ID: <20240108140005.3355316-1-zhangpeng362@huawei.com>
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From: ZhangPeng <zhangpeng362@huawei.com>

The allocation request for swiotlb contiguous memory greater than
128*2KB cannot be fulfilled because it exceeds the maximum contiguous
memory limit. If the swiotlb memory we allocate is larger than 128*2KB,
swiotlb_find_slots() will still schedule the allocation of a new memory
pool, which will increase memory overhead.

Fix it by adding a check with alloc_size no more than 128*2KB before
scheduling the allocation of a new memory pool in swiotlb_find_slots().

Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
---
 kernel/dma/swiotlb.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 33d942615be5..cc92cff02c60 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -1126,6 +1126,9 @@ static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
 	u64 phys_limit;
 	int index;
 
+	if (alloc_size > IO_TLB_SEGSIZE * IO_TLB_SIZE)
+		return -1;
+
 	rcu_read_lock();
 	list_for_each_entry_rcu(pool, &mem->pools, node) {
 		index = swiotlb_pool_find_slots(dev, pool, orig_addr,
-- 
2.25.1